AgSTAR: Biogas Recovery in the Agriculture Sector

AgSTAR promotes the use of biogas recovery systems to reduce methane emissions from livestock waste. In addition to producing biogas, anaerobic digestion systems can also help achieve other social, environmental, agricultural and economic benefits.

Anaerobic Digester Projects in the United States

The colors and sizes of the circles indicate the types and numbers of animals that feed the digester at each project. Click the button (>>) at the top left of the map to toggle the legend. Click on a project to view details.

The increased production is critical because Monument Farms has a small digester and wants to get as much energy out of the digestion as possible. Vermont Hard Cider also benefits, saving on waste transportation and disposal costs since Monument Farms is only three miles from the company.

Nutrient Recovery Systems

WTE-Dallmann
Photo credit DVOWTE-Dallmann, LLC, in Brillion, Wisconsin, is an example of a farm integrating both anaerobic digestion and nutrient recovery into its manure management system to reduce and capture nitrogen and phosphorus from manure. Dallmann’s East River Dairy is host to a 1.7-million gallon capacity digester designed by DVO, Inc. that generates electricity, bedding, fertilizer, and heat. The operation also incorporates an ammonia/nitrogen recovery system after the digester. The recovery system helps to clean the biogas and to remove excess nitrates and ammonia and convert them into a saleable fertilizer. The nutrient recovery system has two high level benefits:

Addresses ammonia emissions from lagoon storage; and

Captures nitrogen in a stable form that can be recycled without atmospheric volatilization.

WTE-Dallman’s system is one of a handful of this type of nutrient recovery systems operating at livestock digesters around the country. This system is sold by DVO, Inc. and portions of the technology were developed in partnership with Washington State University.

Digestate can be separated into liquid and solid components that are land applied as a fertilizer. These products can be used on site reducing material costs or sold to others providing an additional revenue stream.

Environmental Safety

Dane County Digester
Photo Credit Clear HorizonsThe Dane County Community Digester in Vienna, Wisconsin, was built through a partnership among the county, the state, and three Wisconsin dairy farmers. Three adjoining family dairy farms in the towns of Vienna and Dane contribute manure to the digester, which also receives restaurant waste.

The anaerobic digester, owned and operated by Clear Horizons, is achieving the primary goal for which it was designed: keeping phosphorous out of Dane County’s lakes and streams. There have, however, been challenges that Clear Horizons has needed to address in order to make the facility successful. The experiences of Clear Horizons underscore difficulties associated with managing pipeline delivery of manure from multiple farms. Challenges included: unplanned recirculation of liquid digestate from one farm, ineffective sand removal from another and leaking pipelines caused by shifting due to winter freeze. The operation also worked out the kinks of using an innovative advanced centrifugal phosphorus removal system.

Issues aside, the Dane County digester has exported an estimated 90 metric tons of phosphorus from the watershed since 2012, keeping phosphorus from finding its way into Dane County’s streams and lakes.

Environmental Credits

Brubaker Farms protecting the environment for future generationsEnvironmental credits are renewable energy credits (RECs, sometimes called renewable energy certificates) or carbon credits. These are tradable or quantifiable credits that represent generation of a specific amount of electricity (usually 1 megawatt) from renewable energy. RECs are often used by utilities to meet renewable portfolio standards (RPS) or other state standards requiring electricity providers to obtain a minimum percentage of power from renewable resources.

Brubaker Farm in Pennsylvania has an anaerobic digester that produces more than 4 megawatts of electricity a day; equivalent to 150 to 200 homes usage. Brubaker Farm’s uses some of the electricity generated on the farm and at other Brubaker Farm locations; the rest is sold to the local power company and utilized by the neighborhood. Under Pennsylvania’s Alternative Energy Portfolio Standard, the power company pays Brubaker Farm a premium for the renewable energy generated by the digester. Brubaker Farm has sold carbon credits based on methane emission reductions achieved from the anaerobic digester. The Brubaker family works with Vermont-based energy broker NativeEnergy, which specializes in farmer-owned, community-based renewable energy projects to sell carbon credits in a voluntary market. In addition to anaerobic digestion, the farm installed solar panels on the roofs of their barns and has also sold the solar RECs for that energy.